Fiber Optic Rotary Joints allow optical signals carried by fiber optic cables to traverse a rotating interface (for example between the rotating and stationary parts of a piece of equipment). Fiber optics are used in many different applications, and are rapidly replacing traditional copper wiring for communications of signals. Solutions such as slip-rings exist to allow traditional electrical signals to traverse a rotating interface with low loss, but currently existing Fiber Optic Rotary Joints tend to have much higher losses than their electrical counterparts (in addition, existing Fiber Optic Rotary Joints tend to be more complex as well, containing many moving parts such as gear trains and de-rotation prisms—potentially impacting their usable life & reliability).
Applications are numerous, and include rotating radars antennas, photonic control of phased array antennas, instrumentation of rotating equipment (even turbo machinery), data transmission on aircraft, and many other systems. These types of equipment and sensors are used in both the commercial and defense arenas.
Traditional fiber optic rotary joints have usually been built with a de-rotation prism that aims the laser beam from the rotating side of the rotational interface at a consistent stationary point on the stationary side of said interface (see Ames 1992, 1994, etc and Iverson 1978). This de-rotation prism (typically a Dove or Pechan prism) must rotate at ½ the rotational rate of the rotating half of the joint or alternatively can be thought of as rotating at an average of the speed of the two halves (in relative rotation sense). Because of this half speed rotation, these fiber optic rotary joints typically require a reducing gear train and a number of associated bearings, introducing additional sources of misalignment, wear, and failure modes. This patent proposes to utilize magnetic gears (which have been known for over a century—see Armstrong, 1901, Faus 1940), and potentially magnetic bearings as well to essentially suspend these de-rotation optics in mid air, and avoid these concerns—Magnets have actually been used in fiber optic rotary joints that do not include de-rotation optics (such as Spencer & Oliver, 1988), but to the best of our knowledge, magnetic gears and bearings have never been employed with de-rotation optics, which will allow many more channels to pass through the rotary joint simultaneously.
Magnetic gears have been known for many years. Early examples are Faus, U.S. Pat. No. 2,243,555; Iverson, U.S. Pat. No. 4,109,998; and Spencer & Waverly U.S. Pat. No. 4,725,116.
What is needed is a better fiber optic rotary joint.